1. Field of the Invention
The present invention relates to an ink jet printing head and an electronic machine incorporating an ink jet printing head such as, for example, a printer, a word processor, a facsimile machine or a plotter.
2. Description of the Related Art
Conventional ink jet printers are divided broadly into continuance type printers and on-demand type printers. The on-demand type printers, in which ink is injected only when it is necessary, are advantageous in that a simple apparatus suffices, although the responsiveness of the head is low. The on-demand type printers are further divided into electrostatic attraction type printers, in which ink is attracted from the nozzle by electrostatic force, and pressure pulse type printers, in which ink is forced out of the nozzle. The pressure pulse type printers are classified into piezoelectric pressure pulse type printers and bubble pressure pulse type printers. In the piezoelectric pressure pulse type printers, ink is pressurized by a piezoelectric (electrostriction) element. In one-chamber piezoelectric pressure pulse type printers, ink is supplied through a pressure chamber, while two-chamber piezoelectric pressure pulse type printers have a pressure chamber and an ink supply chamber. The one-chamber piezoelectric pressure pulse type printers are further divided into Kyser system printers which have a flat pressure chamber and Soltan system printers which have a cylindrical pressure chamber.
Ink jet printing heads of a Kyser system are mounted into an electronic machine such as a printer or a word processor. As shown in FIG. 1 (partially plan view) and FIG. 2 (partially sectional view), a Kyser system printing head is generally composed of: a multiplicity of individual ink passages 51, each including a supply passage 52, a pressure chamber 53 and an end portion 54 which constitutes a nozzle, provided on a substrate 50 in an array; a diaphragm 60 (omitted in FIG. 1, see FIG. 2) attached to the substrate 50 in such a manner as to cover all the individual ink passages 51; and piezoelectric elements 70 attached to the diaphragm 60 at the positions corresponding to the respective pressure chambers 53 of the individual ink passages 51. In order to apply an electric field to the piezoelectric elements 70, lower electrodes 71 and upper electrodes 72 are provided on the under surfaces and the upper surfaces of the respective piezoelectric elements 70, as shown in FIG. 2, for example.
In such a printing head, an electric field is applied to the piezoelectric element 70 by applying a voltage to the lower electrode 71 and the upper electrode 72 so as to displace the piezoelectric element 70, whereby the corresponding portion of the diaphragm 60 is moved, thereby forcing ink out of the end portion 54 of the corresponding individual ink passage 51.
In this type of printing head utilizing piezoelectric elements, which are represented by a Kyser system printing head, a piezoelectric element is pasted to the corresponding portion of each individual ink passage 51 on the diaphragm 60, as is obvious from FIGS. 1 and 2. As a result, with the increase in the number of individual ink passages 51, the number of manufacturing steps including the production of piezoelectric elements and the process of pasting the piezoelectric elements to the diaphragm increases, which leads to poor productivity and rise in cost. Especially, when the number of individual ink passages 51 is increased and the width thereof and intervals therebetween are reduced in order to increase the printing density, the size of each piezoelectric element is reduced so much that it is difficult to handle each piezoelectric element.